The present invention relates to magnetoresistive devices and, more particularly, to nanopillar magnetoresistive devices.
Nanopillar magnetic devices in which interactions between spin-polarized electrical currents established therein and the magnetic moment of a ferromagnetic material layer therein result in a torque on the magnetization of that ferromagnet through the transfer of angular momentum from that current to that magnetization. These devices formed with a nonmagnetic material provided in the pillar between two ferromagnetic material layers in that pillar have been found to react to electrical currents through these layers by switching the direction of magnetization therein in some circumstances and, in others, by emitting microwaves tunable in frequency by selecting differing values of that current. These effects have been found to occur in such devices where one of the ferromagnetic layers is sufficiently thick to be energetically favorable to nucleate a vortex magnetization state in that layer but there is a desire to be able to select such responses through using the currents established therein to suitably bias the device to yield the desired response.